No timeout for external java process in doGetToolchainModel

## Summary

launches a subprocess and calls without a timeout. A hung or slow JVM process will block Maven indefinitely.

## Location

https://github.com/apache/maven-toolchains-plugin/blob/master/src/main/java/org/apache/maven/plugins/toolchain/jdk/ToolchainDiscoverer.java#L243-L250

## Code

## Problem

without arguments blocks forever until the process completes. If the discovered JDK's java binary is:
- A script that hangs
- A broken/corrupted installation
- An interactive shell
- Extremely slow (e.g., on a network filesystem)

Maven will hang indefinitely with no way to recover other than killing the process.

## Impact

During JDK toolchain discovery, a single problematic JDK installation can cause the entire Maven build to hang permanently. Since discovery scans many directories (including user-controlled paths like , , etc.), a corrupted or slow JDK in any of these locations blocks the build.

## Suggested Fix

Use with a reasonable timeout (e.g., 30 seconds), and if the process times out, destroy it and log a warning:

Start in src/main/java/org/apache/maven/plugins/toolchain/jdk/ToolchainDiscoverer.java at lines 243-250 and inspect how doGetToolchainModel launches the external Java process. Add bounded process handling with cleanup and a warning on timeout, then verify that a hung or slow JDK no longer blocks toolchain discovery.

Written by the indexing model from the issue text.